In applications requiring flow through porous materials such as micro-truss heat exchangers, interfacial pressure loss may represent 7-28% of the component pressure loss.
For example, in one method for providing access to a plurality of hollow tubes the ends of the tubes may be embedded in an epoxy or similar brittle matrix. The epoxy is then fractured in a controlled fashion to reveal a leak-tight fluid interface with the hollow porous material with nearly all pores open to flow.
The interface generated using this method, however, results in significant flow separation, and a vena contracta near the opening of each tube that may be substantially smaller than the inner diameter of the tube. Sharp edges and surfaces normal to the direction of flow cause greater flow disruption and greater component-level pressure loss. The head loss coefficient for flow encountering a right-angle inlet is approximately 0.5, while the head loss coefficient for a filleted inlet is as low as 0.04.
Conventional machining methods for reducing flow disruption by creating a smooth transition at the interface and/or expanding the vena contracta may be prohibitively costly when applied to an interface with a hollow porous material, because such an interface may involve a large number of pores of small diameter.
Thus, there is a need for a cost-effective fluid flow interface to a hollow porous material, which reduces discontinuities and sharp edges and consequently reduces flow disruption, reduces pressure drop for fluid flowing into the hollow porous material, and/or increases pressure recovery for fluid exiting the hollow porous material.